PHP 5 data types
PHP’s data types include the following,
Integer (integer type)
String(String)
Float(Float type),
Boolean(Boolean type)
Array(array)
Object(object)
NULL(null value)
View data type
1. gettype (pass in a variable) can get the type of the variable
2. var_dump (pass in a variable) output variable type and value (most commonly used)
var_dump() is a function. Insert variables between brackets (). This function will print out the data type and also display the length and value of the variable accordingly.
##Integer type (int)
The integer type is divided into :
1. 10-base system 2.8-base system ( Understand, basically don’t use it)
3.16 base (Understand, basically don’t use it)
Octal system declaration: starts with 0, followed by an integer from 0 to 7 (Understand knowledge points) Hexadecimal declaration: Starting with 0x, followed by 0-f, the abcdef of 0x is not case-sensitive. (Understand knowledge points)Integer rules:
· An integer must have at least one digit (0-9) · The integer cannot contain commas or spaces· The integer cannot have a decimal point· The integer can be positive or negative· The integer can be specified in three formats: decimal, hexadecimal System (prefix is ??0x) or octal (prefix is ??0)#Example
In the following example we will test different numbers.
<?php $x = 5985; //十進制 var_dump($x); echo "<br>"; $x = -345; // 負數(shù) var_dump($x); echo "<br>"; $x = 0x8C; // 十六進制數(shù) var_dump($x); echo "<br>"; $x = 047; // 八進制數(shù) var_dump($x); ?>
##String
Strings are all our visible and invisible characters. They are what we say in daily life. What I want to say is: "Li Wenkai is so handsome." ” or “Sister Feng, I love you!” Strings are all the characters that people can see that I want to express.
For example, you can see the characters: I would like to become you, the prince you love, a house, a car and money, in a fairy tale. <html><title></title></html> ^@@@#@ my name is xiaoshenyang and above text, HTML tags, special characters and English, etc., we all Think it is a stringThere are three ways to declare a string in PHP language:
1. Use single quotes to declare
2. Use double quotes to declare
3. Use character delimiters Statement (used when a very large string needs to be entered)
1.Single quote statement Use English half-foot single quotes to wrap the string, as follows:
$zifuchuan= 'I am a single quote';
1. Double quote statement Add double quotes on both sides of the string, as follows:
$zifuchuan= "I am double quotes";
3. Character declaration
1). Write three less than signs (<<<) after the equal sign after the variable.
2). Then write characters after <<< (English uppercase characters are recommended). As in the following example: ABC
3). Then change the line and write any characters you want
4). After writing, go to the top line. At the beginning of the line, write the characters following <<< and a semicolon. As in the following example: ABC;
<?php
$dingjie = <<<ABC
If
It must be here Roll the calf
? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ?Far, get as far away from me</h1>
ABC;
?>
##Example
In the following example, we will output a string. <?php
$x = "Hello world!";
echo $x;
echo "<br>";
$x = 'Hello world!';
var_dump($x) ;
?>
##Float
The so-called floating point type can be understood as: the decimal in our mathematics.
Example
We use echo and Print to output floating point types respectively <?php
//聲明變量fudian的值為12121.3132
$fudian = 12121.3132;
echo $fudian;
echo "<br>";
//聲明變量$fl 的值為0.8873
$fl = 0.8873;
var_dump($fl);
?>
echo directly outputs 12121.3132, and var_dump The output is 0.8873, and it also shows that the type of variable $fl is float.
##Boolean type(bool)
The Boolean type is: true and false. The translation of true and false in English is: · true (true)
· false (false)
Therefore, we can do this in the PHP code statement.
<?php
//Declare a variable (Pinyin) as Boolean
$buer = true;
//State a variable (English)
$bool = false;
?>
Note: Do not add quotation marks around for true and false.
#Array
<?php
$cars=array("Volvo","BMW","SAAB");
var_dump($cars);
?>You will learn more about arrays later in this tutorial. Object (Object)
#NULL (null value)<?php class Car
{
var $color;
function Car($color="green") {
$this->color = $color;
}
function what_color() {
??????????? return $this->color;
??????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????Knowledge about objects, just know it now
Empty means null in English, which means nothing. Null is not false, not 0, and not a space.
There are three main situations that will produce a null type: 1. The value of a variable explicitly specified as NULL through variable assignment
2. A variable has no Give any value
3. Use the function unset() to destroy the variable
Let’s demonstrate it with code
<?php //聲明變量為null $n = null; var_dump($n); //var_dump顯示輸出變量$meiyou，看看結果是什么？ var_dump($meiyou); //聲明一個變量$iphone的值為字符串的手機 $iphone = '手機'; //unset銷毀掉一個變量 unset($iphone); var_dump($iphone); ?>
Next we will explain two things related to null Functions, these two functions are very commonly used.
empty()
You can pass a variable into the middle of the brackets. If the value of this variable is false or null, it returns true.
Example<?php
header("Content-type:text/html;charset=utf-8"); //設置utf-8編碼
$apple = null;
if(empty($apple)){
echo '執(zhí)行了真區(qū)間';
}else{
echo '行了假區(qū)間';
}
?>
##The above experiment proves that $apple is null. Place the apple in the middle of empty. The result is a true interval.
isset()You can pass one or more variables into the middle of the brackets, and separate variables with commas. As long as there is a variable that is null, it returns false. Otherwise, returns true.
Example
<?php $one = 10; $two = false; $three = 0; $four = null; $result = isset($one , $two , $three , $four); //執(zhí)行看看結果，是不是 var_dump($result); ?>
##unset()The function of this function is to destroy variables. Insert the variable name you want to destroy between the unset (variable) brackets, and the variable will be destroyed.
